Signals are transmitted between devices, which send or receive signals, and transmission lines via a connector provided at either the output end or the input end of a device. In most of these types of signal transmission methods, a physical interface is previously prescribed as a standard. Representative physical interfaces are applicable to connector mechanical structures and dimensions, signal amplitude, impedance, frequency characteristics, loss, and the like.
Recently, along with the development of the application of broadcasting technology using High Definition Television (HDTV) signals, there has been an increase in examples in which high-speed and wideband pulse signal strings are transmitted between devices and transmission lines. When transmitting these types of high-speed and wideband pulse signal strings, it is important to pay close attention to electrical characteristics such as frequency characteristics, signal levels, and even return loss.
In the past, connectors were used to try to improve frequency and reflection characteristics by making the connector itself a four-terminal circuit network to try to avoid degradation of the signals as they passed through the connector acting as a passive component connecting circuits inside a device and a transmission line.
However, since a connector is basically a passive circuit, when signals are transmitted to the transmission line, the connector is electrically affected by the driver circuits inside the device. On the other hand, when the connector receives signals from the transmission line, the connector is electrically affected by the circuit inside the device acting as a connector load. Also, the connector may be affected by another transmission line (internal wiring) connected between the connector and a circuit inside the device.
In this way, even if the characteristics of the connector itself as a four-terminal circuit network are suitable, the connector is electrically affected by the transmission line and the circuits inside the device to which the connector is joined. Thus, the connector must also be considered when designing the inside of the device. However, high-speed and wideband pulse signals are sensitive to the effects of parasitic elements and so the design of the inside of the device must take into account technical know-how on component mounting, circuit pattern, and the like. Therefore, the performance of the device depends upon the designer and may vary greatly regardless of whether the device is designed and assembled according to the same circuit drawings.
An active connector with an active circuit such as an amplifier provided inside the connector is disclosed for example in Japanese Unexamined Patent Application Publication No. 2007-258125. However, the aforementioned document does not disclose that the active connector avoids mutual influences between input and output signals thereof designed to be connected between circuit boards.